China has sentenced a leading academic to 20 years in prison for allegedly leaking “high level” state secrets, a human-rights group in Hong Kong reported today.

The group, the Information Center for Human Rights and Democracy, said that Lu Jianhua, 46, a sociologist at the Chinese Academy of Social Sciences, a government think tank, was tried in a closed hearing on August 16. The Hong Kong group said the verdict and sentence were not handed down until Monday. Mr. Lu’s family was not allowed to choose a defense lawyer, and his wife was prevented from attending his trial, the rights group said.

No details of the prosecution have been released by the Chinese government, as is the practice in cases involving so-called state secrets. Mr. Lu’s conviction appears to be connected to a case involving Ching Cheong, a reporter in Hong Kong for Singapore’s Straits Times. Mr. Ching was sentenced this year to five years in prison for allegedly spying for Taiwan, a charge he has denied.

A Paris-based group, Reporters Without Borders, called on academics to “rally to Lu’s defense.” “Applying the state-secrets law with the utmost severity in Lu’s case constitutes a very grave violation of press and scientific freedom,” the organization said in a news release. “It dramatically highlights the violence with which the Communist Party cracks down on researchers and journalists who try to work and publish independently.”

Mr. Lu published some 70 articles in The Straits Times, and the Information Center for Human Rights and Democracy quoted unnamed Chinese intelligence officials as saying that four of the essays, published in May 2004, contained state secrets. The Communist Party often uses such vague charges to silence critics.

Mr. Lu was the editor of an annual report on the social situation in China published by the Chinese Academy of Social Sciences, and he regularly appeared on state-television talk shows before his arrest, in April.